The invention relates to a process for dewatering an aqueous organic solution.
Processes are known for producing high concentration organic solutions such as alcohols useful in the production of alternative fuels. For instance, ethanol suitable for blending with gasoline generally has a concentration of between about 95% and about 100% ethanol by weight and less than about 1% water by volume. Known processes for dewatering ethanol solutions to achieve suitable concentrations include conventional distillation of a fermentation broth to raise the concentration of the broth, until an azeotropic solution is formed. For example, the concentration of ethanol in the broth may be raised using conventional distillation until an azeotrope is formed. The distillation process can be followed by further processing to further remove water from the solution. Such further processing includes distilling at lower than atmospheric pressure in order to derive more ethanol-rich solutions, extractive distillation in which the ethanol solution further includes a separation solvent or extracting agent having a high boiling point and being miscible with the ethanol solution which avoids formation of an azeotrope, and entrainer addition in which the ethanol-water azeotrope can be broken by the addition of a small quantity of benzene or cyclohexane which is followed by a fractional distillation process. Unfortunately, these processes are highly energy intensive. A less energy intensive, alternative process for dewatering solutions uses a highly water selective pervaporation membrane, although heat input is required.
It would be desirable to have a commercially viable, more energy-efficient process for dewatering an organic solution.